Simple blockchain realisation with Flask API.
- main class
Blockchain:
class Blockchain(object):
def __init__(self):
self.chain = []
self.current_transactions = []
self.nodes = set()
# Generate genesis block
self.new_block(100, previous_hash=1)
def new_block(self, proof, previous_hash=None):
"""Creates new block in the Blockchain.
Arguments:
proof {int} -- Block's proof given by the Proof-of-Work algorithm.
Keyword Arguments:
previous_hash {str} -- Previous block's hash (default: {None}).
Returns:
dict -- The Block.
"""
...
def new_transaction(self, sender, recipient, amount):
"""Creates new transaction to go to the next mined block.
Arguments:
sender {str} -- Address of the transaction's sender.
recipient {str} -- Address of the transaction's recipient.
amount {int} -- Transaction's amount.
Returns:
int -- The index of the block that will hold this transaction.
"""
...
@staticmethod
def hash(block):
"""Creates a SHA-256 hash of a block.
Arguments:
block {dict} -- Block.
Returns:
str -- Hash string.
"""
...
@property
def last_block(self):
...
def proof_of_work(self, last_proof):
"""Simple Proof-of-Work algorithm.
- Find a number p' such that hash(pp') contains leading 4 zeroes,
where p is the previous p'
- p is the previous proof, and p' is the new proof
Arguments:
last_proof {int} -- Last valid proof.
Returns:
int -- Proof.
"""
...
@staticmethod
def valid_proof(last_proof, proof):
"""Validates the Proof.
Does hash(last_proof, proof) contain 4 leading zeroes?
Arguments:
last_proof {int} -- Last valid proof.
proof {int} -- Current proof.
Returns:
bool -- True - if correct, False - otherwise.
"""
...
def register_node(self, address):
"""Adds a new node to the list of nodes.
Arguments:
address {str} -- Address of node. Eg. 'http://192.168.0.5:5000'.
"""
...
def valid_chain(self, chain):
"""Determines if a given blockchain is valid.
Arguments:
chain {list} -- A blockchain.
Returns:
bool -- True if valid, False - if not.
"""
...
def resolve_conflicts(self):
"""This is our Consensus Algorithm.
It resolves conflicts by replacing our chain
with the longest one in the network.
Returns:
bool -- True if our chain was replaced, False if not.
"""
...- proof of work -- validates the new proof if SHA-256 hash of new proof and last proof has four leading zeroes:
@staticmethod
def valid_proof(last_proof, proof):
"""Validates the Proof.
Does hash(last_proof, proof) contain 4 leading zeroes?
Arguments:
last_proof {int} -- Last valid proof.
proof {int} -- Current proof.
Returns:
bool -- True - if correct, False - otherwise.
"""
guess = f'{last_proof}{proof}'.encode()
guess_hash = hashlib.sha256(guess).hexdigest()
return guess_hash[:4] == '0000'/mine-- mines new block/transactions/new-- creates new transaction for the next mined block/chain-- lists current chain/nodes-- lists known blockchain nodes/nodes/register-- register new node/consensus-- checks all known nodes and compares own chain with other to find the longest valid chain